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Influence of metal contents on the characteristics of biodiesel and petrol blends as transportation fuel
Author(s)
Simbi, Ines
Date Issued
2021
Type
Thesis
Publisher
Cape Peninsula University of Technology
Abstract
The development of renewable energy seems to be the key player in addressing global
climate crisis, caused by the global warming and climate change. To produce less
emissions, new engine systems have been developed i.e., petrol compression ignition
engines, which promise to produce less emissions, while generating high efficiency, and
facilitating economic, social, and environmental sustainability. With the novelty of
blending biodiesel with petrol, the challenges caused by biodiesel, and petrol individually,
are lessened. Nevertheless, biodiesel’s proneness to corrosion and degradation overtime,
due to its chemical nature and storage conditions require continuous evaluation.
In the initial part of this study, the bi-functional catalyst (75%CaO/25%Al2O3) was
synthesised via adjusted wet impregnation method. Results showed that, the catalyst
presented enhanced activity, good porosity, and type H1 desorption hysteresis loop, with
the high surface area and the pore diameter of 13.006 m2/g, 24.0371 nm. The catalyst
characterisations were conducted through BET, XRD, FTIR and SEM. The obtained bifunctional
catalyst favoured the transesterification reaction of high free fatty acids
feedstocks, with high yields of above 98% of methyl esters in biodiesel produced from
waste sunflower oil. With the use of GC, fatty acids compositions of waste sunflower and
waste palm oils were determined. The results also showed that the chemical composition
of these different feedstocks i.e., degree of saturation, chain length, produced biodiesels
with varying fuel properties. While sunflower biodiesel indicated better viscosity, palm
biodiesel had excellent oxidation stability. Additionally, sunflower biodiesel met the
international biodiesel specifications, with the exception of increased Ca concentration
within the biodiesel, as a result of CaO/Al2O3 catalyst use in the biodiesel synthesis. This
soft metal, along with Mg, K were introduced in the biodiesel through the synthesis
process. While soil, seed, fertiliser, and contamination in the vegetable oils, may have
contributed to the high content of P, and trivial Fe, Al, and Zn. The use of ICP - OES
allowed for the determination of these metals.
To commercialise biodiesel, optimisation can be performed in reducing the cost and time
necessary to produce biodiesel. After optimising sunflower biodiesel using response
surface methodology and central composite design, the optimal reaction conditions
observed were 5 h for reaction time, 60 C for temperature and 2.5wt% for catalyst weight.
With the use of a linear regression model that had 95 % confidence, the predicted and
experimental yields were confirmed to be comparable.
In accessing fuel quality of biodiesel and the biodiesel-petrol blends, analysis of the
viscosity, acidity, oxidation, density, volatility, moisture content, cetane number, metal
contamination and particulate matter were conducted. Palm biodiesel had an increased
thermal stability which rendered the palm biodiesel-petrol blended fuels superiority over
the sunflower biodiesel-petrol blends. The blended fuels were observed to have enhanced
fuel characteristics, better than pure petrol, increasing with increase in biodiesel content
with 75% petrol 25% biodiesel (PB25) showing quality like petrodiesel. The addition of
petrol into the biodiesel diminished the Ca concentrations, and obstructed moisture
absorption, while improving low temperature fluidity loads, air-fuel mixing, and
characteristics of good performance with high efficiency. Sunflower biodiesel-petrol blends
were observed to be less acidic, have more energy content and subsequently more power.
While palm biodiesel-petrol blends had more thermal stability and better cold start.
Moreover, addition of petrol reduced particulate matter of sulphates.
In the final part of this study, the effect of Cu, Fe and Zn on the characteristics of fuel
quality were evaluated for the purpose of the storage and transportation of biodiesel and
the biodiesel-petrol blends. From the results obtained for pure biodiesel, the highest
degradation was caused by exposure to Fe concentrations, while degradation in the
biodiesel-petrol blends was caused by exposure to Cu. Sunflower biodiesel-petrol blends
degraded in order of Fe > Cu > Zn, while palm biodiesel-petrol blends were degraded by
Cu > Fe > Zn, and with Cu affecting pure palm biodiesel the most. Increase in oxidation
instability for biodiesel-petrol blends was due to rise in Cu concentrations. The fuel quality
was observed to decrease the most in palm biodiesel and palm biodiesel-petrol blends.
climate crisis, caused by the global warming and climate change. To produce less
emissions, new engine systems have been developed i.e., petrol compression ignition
engines, which promise to produce less emissions, while generating high efficiency, and
facilitating economic, social, and environmental sustainability. With the novelty of
blending biodiesel with petrol, the challenges caused by biodiesel, and petrol individually,
are lessened. Nevertheless, biodiesel’s proneness to corrosion and degradation overtime,
due to its chemical nature and storage conditions require continuous evaluation.
In the initial part of this study, the bi-functional catalyst (75%CaO/25%Al2O3) was
synthesised via adjusted wet impregnation method. Results showed that, the catalyst
presented enhanced activity, good porosity, and type H1 desorption hysteresis loop, with
the high surface area and the pore diameter of 13.006 m2/g, 24.0371 nm. The catalyst
characterisations were conducted through BET, XRD, FTIR and SEM. The obtained bifunctional
catalyst favoured the transesterification reaction of high free fatty acids
feedstocks, with high yields of above 98% of methyl esters in biodiesel produced from
waste sunflower oil. With the use of GC, fatty acids compositions of waste sunflower and
waste palm oils were determined. The results also showed that the chemical composition
of these different feedstocks i.e., degree of saturation, chain length, produced biodiesels
with varying fuel properties. While sunflower biodiesel indicated better viscosity, palm
biodiesel had excellent oxidation stability. Additionally, sunflower biodiesel met the
international biodiesel specifications, with the exception of increased Ca concentration
within the biodiesel, as a result of CaO/Al2O3 catalyst use in the biodiesel synthesis. This
soft metal, along with Mg, K were introduced in the biodiesel through the synthesis
process. While soil, seed, fertiliser, and contamination in the vegetable oils, may have
contributed to the high content of P, and trivial Fe, Al, and Zn. The use of ICP - OES
allowed for the determination of these metals.
To commercialise biodiesel, optimisation can be performed in reducing the cost and time
necessary to produce biodiesel. After optimising sunflower biodiesel using response
surface methodology and central composite design, the optimal reaction conditions
observed were 5 h for reaction time, 60 C for temperature and 2.5wt% for catalyst weight.
With the use of a linear regression model that had 95 % confidence, the predicted and
experimental yields were confirmed to be comparable.
In accessing fuel quality of biodiesel and the biodiesel-petrol blends, analysis of the
viscosity, acidity, oxidation, density, volatility, moisture content, cetane number, metal
contamination and particulate matter were conducted. Palm biodiesel had an increased
thermal stability which rendered the palm biodiesel-petrol blended fuels superiority over
the sunflower biodiesel-petrol blends. The blended fuels were observed to have enhanced
fuel characteristics, better than pure petrol, increasing with increase in biodiesel content
with 75% petrol 25% biodiesel (PB25) showing quality like petrodiesel. The addition of
petrol into the biodiesel diminished the Ca concentrations, and obstructed moisture
absorption, while improving low temperature fluidity loads, air-fuel mixing, and
characteristics of good performance with high efficiency. Sunflower biodiesel-petrol blends
were observed to be less acidic, have more energy content and subsequently more power.
While palm biodiesel-petrol blends had more thermal stability and better cold start.
Moreover, addition of petrol reduced particulate matter of sulphates.
In the final part of this study, the effect of Cu, Fe and Zn on the characteristics of fuel
quality were evaluated for the purpose of the storage and transportation of biodiesel and
the biodiesel-petrol blends. From the results obtained for pure biodiesel, the highest
degradation was caused by exposure to Fe concentrations, while degradation in the
biodiesel-petrol blends was caused by exposure to Cu. Sunflower biodiesel-petrol blends
degraded in order of Fe > Cu > Zn, while palm biodiesel-petrol blends were degraded by
Cu > Fe > Zn, and with Cu affecting pure palm biodiesel the most. Increase in oxidation
instability for biodiesel-petrol blends was due to rise in Cu concentrations. The fuel quality
was observed to decrease the most in palm biodiesel and palm biodiesel-petrol blends.
Additional information
Thesis (MEng (Chemical Engineering))--Cape Peninsula University of Technology, 2021
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